C / C++ / MFC Discussion Boards

Re: Heap ,Stack allocation question

Richard MacCutchan5-Mar-14 4:48

Richard MacCutchan

5-Mar-14 4:48

That is correct, as far as I recall; MFC classes clean up after themselves.

Re: Heap ,Stack allocation question

econy5-Mar-14 5:04

econy

5-Mar-14 5:04

I try to use delete myMap, IDE shows cannot convert from 'CMap' to 'Void*'.

Re: Heap ,Stack allocation question

Richard MacCutchan5-Mar-14 5:29

Richard MacCutchan

5-Mar-14 5:29

You need to show us your code, we cannot guess what you have done.

Re: Heap ,Stack allocation question

econy5-Mar-14 9:06

econy

5-Mar-14 9:06

class A
{
	private:
		A m_Map;
	public :
		A();
		~A();
};

//Constructor
A::A()
{
	m_Map.InitHashTable(MAP_LEN);
}

A:~A()
{
	delete m_ConfigMap;   //This statement triggered error message
}

error C2440: 'delete' : cannot convert from 'CMapStringToString' to 'void *'

Re: Heap ,Stack allocation question

Richard Andrew x645-Mar-14 10:10

Richard Andrew x64

5-Mar-14 10:10

I see two issues here:

1. Where is m_ConfigMap declared?

2. You have m_Map declared as an A. Is that what you meant?

The difficult we do right away...
...the impossible takes slightly longer.

Re: Heap ,Stack allocation question

econy5-Mar-14 15:28

econy

5-Mar-14 15:28

sorry, yes, m_configMap should be m_Map.

Re: Heap ,Stack allocation question

Richard MacCutchan5-Mar-14 22:24

Richard MacCutchan

5-Mar-14 22:24

That code makes no sense. You declare m_Map as an object of class A. You then try to call InitHashTable on it in the constructor, even though that function is not declared anywhere. Finally you try to delete m_ConfigMap which also is not declared anywhere.

#include cpp file - how it works?

Vaclav_5-Mar-14 3:26

Vaclav_

5-Mar-14 3:26

I am using DirectShow "common" dshowutil.cpp file and I just found this, to me new , usage of #include directive.
It only works if included in a source file where its function(s) are used.
Makes sense.
Elsewhere the linker generates multiple definitions, so it must be included somewhere else, I did not search for it.

Here is the #include:

#pragma message("Common DirectShow support ")
#include "D:\00\0 SDK\DIrectShow 8.1 SDK\samples\Multimedia\DirectShow\Common\dshowutil.cpp"

And here is the usage sample:

TRACE("\nFind input and output pins and connect them");
IPin * pCapOut = GetOutPin( pDocument->pC_Graph->gcap.pVCap, 0 );

In my view it prepends the working source file.

I would like some other explanations from the group.

Is such usage of including cpp file common?

Thanks for your time.
CHeers
Vaclav

Re: #include cpp file - how it works?

Jochen Arndt5-Mar-14 4:12

Jochen Arndt

5-Mar-14 4:12

The #include statement is a preprocessor directive. The preprocessor is reading input files, processes his commands, and writes the result to an output file (source file name with extension 'i'). The #include statement just inserts the processed content of another file.

When invoking the compiler, the preprocessor is started first for each source file and the created preprocessed file is the input for the compiler. After compilation the file is deleted (the deletion can be omitted by passing a compiler option flag on the command line or setting it in the VS project setting).

It is not very common to include other source files but allowed.

Re: #include cpp file - how it works?

Richard MacCutchan5-Mar-14 4:44

Richard MacCutchan

5-Mar-14 4:44

Vaclav_Sal wrote:
In my view it prepends the working source file

But that is perfectly acceptable as long as all required include files are added within that cpp file. It is just the same as adding some extra functions at the top of a source file before the #include statements required by the remainder of the source.

Re: #include cpp file - how it works?

Vaclav_5-Mar-14 5:10

Vaclav_

5-Mar-14 5:10

So are the include cpp functions global only to the attched cpp which is basically an object / class?

Is that the reason I was getting multiple definitions when I included it in StdAfx header?

I did not try to access the preprocessed functions outside the class. It should not work.

Actually found that I was telling the DirectShow to add another filter and had no intermediate filter / pins to connect to. Fixed that so I do not need to do the connections manually.

Re: #include cpp file - how it works?

Richard MacCutchan5-Mar-14 5:31

Richard MacCutchan

5-Mar-14 5:31

Without seeing all the code in the included file it is impossible to answer that.

Re: #include cpp file - how it works?

leon de boer9-Mar-14 8:51

leon de boer

9-Mar-14 8:51

You are spot on Val you will get multiple inclusions if the file is multiple included, unless the file contains standard one time load #ifdef protection around the top and bottom

If the programmer knew what they were doing they would have something that looks like this top/bottom of include file

// PROTECTION TO STOP MULTIPLE UNIT LOADING
#ifndef _FILENAME_ID_
#define _FILENAME_ID_

#endif

It is still quite common in a very specific circumstance .. can you think what it might be Smile | :)

I will give you a hint:

I know the old version of windows.h from Microsoft did it but they changed it all a few years ago when they broke that unit up. You will probably also find it on the android source unless they worked there way around it.

CMap class questions [Solved]

econy5-Mar-14 2:14

econy

5-Mar-14 2:14

I use a CmapStringToString object, put over 10000 key-value pairs into the object.

But I use:
test1 = mStrMap.GetCount();
test2 = mStrMap.GetHashTableSize();

try to get the map size.

test1 = 0x00000299
test2 = 0x00000011

I wonder what the meaning of GetCount(), and GetHashTableSize();

modified 5-Mar-14 11:12am.

Re: CMap class questions

CPallini5-Mar-14 2:47

CPallini

5-Mar-14 2:47

With the following code

C++

CMapStringToString mss;
//mss.InitHashTable(32767);


for (int i=0; i<10000; ++i)
{
    CString k,v;
    k.Format("%05d", i);
    v.Format("Foo%02d", i%100);
    mss[k] = v;
}
int count = mss.GetCount();
int hsize = mss.GetHashTableSize();

I get:
count = 10000
hsize = 17

I don't know what exactly GetHashTableSize returns, the documentation is not much detailed about.

Veni, vidi, vici.

Re: CMap class questions

econy5-Mar-14 3:18

econy

5-Mar-14 3:18

My fault, checked again, GetCount() works well for me too.

Re: CMap class questions

Richard MacCutchan5-Mar-14 3:13

Richard MacCutchan

5-Mar-14 3:13

See http://msdn.microsoft.com/en-us/library/9ah6bd2h.aspx[^] for details about the hash table size. Are you certain you added 1000 items?

Re: CMap class questions

econy5-Mar-14 3:44

econy

5-Mar-14 3:44

Sorry, my fault, checked again, GetCount() return value is right.
but don't know what is the meaning of GetHashTableSize();

Re: CMap class questions

Richard MacCutchan5-Mar-14 4:37

Richard MacCutchan

5-Mar-14 4:37

That's why I gave you a link to the MSDN page that explains it.

Re: CMap class questions

econy5-Mar-14 4:07

econy

5-Mar-14 4:07

Determines the number of elements in the hash table for the map. // msdn: GetHashTableSize();
Retrieves the number of elements in the map. //msdn: GetCount()

And I read some articles, they say Hashmap is equivalent to Hashtable.

So, what is the difference between GetCount() and GetHashSize() confused me

Re: CMap class questions

Richard MacCutchan5-Mar-14 4:39

Richard MacCutchan

5-Mar-14 4:39

econy wrote:
So, what is the difference between GetCount() and GetHashSize()

GetCount returns the number of elements in the Map, e.g. 1000. GetHashSize gives the size of the Hash table that is used to manage the Map; in most cases this information is not useful to you.

if/else, expression can not be used as a function. C program

cstudent14-Mar-14 20:37

cstudent1

4-Mar-14 20:37

Hi everyone, I am taking my first programming class and am at a loss on this program. Any tips for making this wrk? Thanks!

#include<stdio.h>
int main()

{
int month,day,opselect;

printf("\nEnter a month between 1 and 12: \n ");
scanf("%d",&month);

while (month < 1 || month > 12)
{
printf("Error the month entered is not valid.\n");
printf("\nEnter a month between between 1 and 12: ");
scanf("%d",&month);
}

printf("The month accepted is %d\n",month);
printf("\nEnter a day between 1 and 31: \n ");
scanf("%d",&day);
scanf("%d",opselect);

switch (opselect)

if (month=2)
(day < 1 || day > 28);

{
printf("Error the day entered is not valid.\n");
printf("\nEnter a day between 1 and 28\n");
scanf("%d,&day");
}

else (month=4,6,9,11)
(day < 1 || day > 30);

{
printf("Error the day entered is not valid.\n");
printf("\nEnter a day between 1 and 30\n");
scanf("%d,&day");
}
return 0;
}

errors are "else w/o a previous if"
and "expression can not be used as a function"

Re: if/else, expression can not be used as a function. C program

Jochen Arndt4-Mar-14 21:12

Jochen Arndt

4-Mar-14 21:12

You code contains many errors:

The scanf() call for opselect misses the ampersand &.
There is an empty switch statement.
C/C++ comparisons use two equal signs.
This is a complete if sequence:

C++

if (month=2)
    (day < 1 || day > 28);

Because there is other code following before the else, the compiler can not found any corresponding if and generates an error. The code following the if statement is an expression (day < 1 || day > 28). But the compiler expects a statement or a function call and generates another error.

As already noted, comparisons use two equal signs. Your code assings the value 2 to month and the if condition is always true.

I guess you want something like this:

C++

if (month == 2 && (day < 1 || day > 28))
{
// some code
}
else if ((month == 4 || month == 6 || month == 9 || month == 11) && (day < 1 || day > 30))
{
// some code
}

Re: if/else, expression can not be used as a function. C program

cstudent15-Mar-14 7:14

cstudent1

5-Mar-14 7:14

Thanks, I am trying to implement your suggestions here is what I currently have..

#include <stdio.h>
#define MAXCOUNT 10

int main ()
{
int opselect;
int day, month;

printf("Enter a month between 1-12 :");
scanf("%d", &month);
printf("Enter a number for the day of the month");
scanf("%d", &day);
scanf("%d", &opselect);

switch (opselect) {

case 1:
if (month==2 && (day < 1 || > 28))
{printf("\nEnter a day between 1 and 28: \n ");
scanf("%d",&day);
}

case 2:
else if (month==4 || month==6 || month==9 || month==11)&&(day < 1 || day > 30))
{printf("\nEnter a day between 1 and 30: \n ");
scanf("%d",&day);
}

case 3:
else if (month==3 || month==5 || month==7 || month==10 || month==12)&&(day < 1 || day > 31))
{printf("\nEnter a day between 1 and 31: \n ");
scanf("%d",&day);
}

printf("The day accepted is %d\n",day);

return 0;
}

I am getting a ton of errors here, expected primary-expression before else, expected; before else.

What I am trying to do is based on the month input prompt for a the proper number of days in the month(2=28, 1=31 etc)and get in error message if you enter the wrong days(29 in Feb for example)

Re: if/else, expression can not be used as a function. C program

Jochen Arndt5-Mar-14 7:40

Jochen Arndt

5-Mar-14 7:40

You are mixing a switch statement with if - else statements. That is not allowed. What is the opselect for? It seems unnecessary.

A more sophisticated solution would use an own function that checks if a day/month combination is valid:

C++

if (!CheckDate(month, day))
{
    printf("\nInvalid day/month combination. Please enter a valid day:\n");
    scanf("%d",&day);
}

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